Electrical slider switch



United States Patent 3,378,653 ELECTRICAL SLIDER SWITCH Scott Lynn, Walnut Creek, Calif., and Jack N. WllSJIl,

Kaiama, Wash, assignors to The Dow Chemical Comparry, Midland, Mich, a corporation of Delaware Filed Dec. 21, 1966, Ser. No. 603,622 6 Claims. (Cl. 200-16) ABSTRACT UP THE DISCLOSURE The invention concerns a switch for low voltage, high current application. It is a sliding contact type switch, totally enclosed and submerged in oil, has few parts and is compact. The switch is especially well adapted to be connected in ganged assemblies and for operation by air cylinder or similar means.

Baekground of the invention This invention relates to electrical switches and particularly to high amperage, low voltage shunt circuit switches.

Numerous types of switches for use in low voltage, high current applications are known. Such switches are used in connection with thetoperatioiof electrolytic cells, such as chlorine-caustic cells, for example, and are thus subjected to conditions which tend to result in corrosion of the switches. Further, such switches and/ or their operating mechanisms tend to be bulky in relation to the current carrying capacity of the switches. Another problem with prior art switches is that many of them require special plating of the electrodes and contact areas of the switches. In addition reliability is often a problem, since downtime" of equipment while switches are being repaired is expensive from a plant operations standpoint.

Accordingly, a principal object of this invention is to provide an improved low voltage, high current switch.

Another object of this invention is to provide an improved longer lived low voltage, high current switch.

A further object of this invention is to provide an improved low voltage, high current switch which has high current carrying capacity in proportion to its bulk.

An additional object of this invention is to provide an improved low voltage, high current switch which is not subject to atmospheric corrosion.

An ancillary object of this invention is to provide an improved low voltage, high current switch which is well adapted for ganged operation.

Summary of the invention In accordance with this invention there is provided a multiple contact slide bar switch which is totally enclosed with the switch elements immersed in fluid. Balanced spring means are provided for directing the movable contacts against the fixed contacts at a predetermined pressure. Longitudinal movement of the bar of about one inch opens or closes the switch.

Brief description of the drawing The invention, as well as additional objects and advantages thereof, will best be understood when the following detailed description is read in connection with the accompanying drawing, in which:

FIG. 1 is a plan view, with the switch cover removed, of a switch made in accordance with this invention;

FIG. 2 is a sectional View taken along the line 22 of FIG. 1, and

FIG. 3 is a sectional view taken along the line 3-3 of FIG. 1.

3,373,653 Patented Apr. 16, 1968 Description of the preferred embodiments apparatus 10 comprises a first contact plate 12, a second I contact plate 14, switch frame 16, and reciprocatable shaft 18 having a plurality of contact leaf assemblies 20 coupled thereto.

The first contact plate is a generally flat, rectangularly shaped plate having an array of bores 22 adjacent to the peripher of the plate. The thickness of the plate is at least sufiicient to provide rigidity to the plate during operation of the switching apparatus.

The first contact plate 12 also has an array of spaced apart rectangularly shaped depressions 24 in the surface 26 thereof which faces the shaft 18. The depressions 24 are disposed perpendicularly to the longitudinal axis of the plate (and to the axis of the shaft 18), and have length, width, and depth such that when the shaft 18 is in the open switch position, to be described later, the contact leaf assemblies 29 are out of contact with the first contact plate 12.

The second contact plate 14 is shaped generally as is the first contact plate except that its surface 28 which faces the shaft 18 is flat and contains no depressions like the depressions 24 in contact plate 12. The plate 14 has an array of bores 30 adjacent to its periphery.

The switch frame 16 has a rectangular outer configuration when viewed in plan, and is hollow except for the outer wall structure 32. The frame 16 is sandwiched be tween the first and second contact plates and is insulated from the first contact plate 12 by means of an insulating gasket plate 34 which is sandwiched between compression gasket seal elements 36, 38. A compression gasket 40 extends between the frame 16 and the second contact plate 14. Each of the compression gasket elements and the insulating gasket plate 34 is generally flat, as are the top and bottom of the frame 16 and the surfaces of the contact plates facing the top and bottom of the frame 32. The width of the gasket elements and the insulating gasket plate is at least as wide as the contacting surfaces of the frame and may be somewhat Wider provided they do not contact or interfere with the movement of the contact leaf assemblies 20.

The first and second contact plates 12, 14 are secured to the frame 32 in liquid tight manner by means of the bolts 42, 44, respectively, which extend through the arrays of bores 36, 22, respectively. It should be noted that a flanged insulating sleeve separates each of the bolts 42 from the contact plate 12, thus, with the insulating plate 34, preventing electrical contact between the frame 16 and the contact plate 12.

The switching apparatus in FIG. 1 shows a ganged array of two switches but the view in FIG. 2, is limited to a single switching assembly. Thus, the device of FIG. 1 would have a frame which, in essence, is two frames of the above described type joined end to end with common end walls.

The frame 32 has, as shown in FIG. 3, oil inlet and outlet lines 48, 50, respectively. In the event the frame end wall 52 shown in FIG. 2 is the common end wall of ganged switching assemblies as shown in FIG. 1, bores 54, 56 are provided to permit the circulation of oil through the various gangs of the apparatus.

Each end wall 52, 53 of the frame 16 has an axially 3 liquid-tight seal between the shaft 18 and each bore 60, 62.

The shaft 18 carries along its length within the frame 16 a plurality of contact leaf assemblies 20 arranged in side by side, usually abutting relationship and held in fixed position along the shaft by end plates 72, 74 which are pinned or otherwise fixedly secured to the shaft 18.

The means for moving the shaft 18 back and forth in an axial direction is disposed externally of the switching assembly, but for the sake of simplicity and compactness in the drawing, a suitable pneumatically driven piston 76 in an air cylinder assembly 78 having air inlet and outlet control lines 80, 82 drives a throw arm 84. The arm 84 is coupled to a pivot, as at 86, intermediate of its ends and is coupled at one end to the shaft 18 by means of collar 88.

Each of the contact leaf assemblies comprises a sleeve 90 which fits slidably over the shaft 18. A contact leaf elelengthwise of the arms and bows towards the adjacent contact plate 12, 14, respectively.

A clamp element 102 which is a plate-like element having a bore 104 which adapts the element to be fitted in slidable relationship around the shaft 18 and flanges 106, 108 at each end which extend towards the contact leaf 92. The outer ends of the arm elements of the contact leaf 92 fit under and are prevented from further expansion outwardly by the flanges 106, 108.

A pressure bar 110, 112 which is as long as the length of each arcuate part of the arm elements 98, 100, respectively, has a semi-circular transverse cross sectional configuration. One of the bars 110, 112 is fitted against each arcuate part of the arms 98, 100 with the curved surfaces of the parts abutting each other.

As may be seen in FIG. 3, each of the pressure bars 110, 112 has a bore 114, 116 and 118, 120, respectively, extending inwardly from the fiat surface of the bar which is opposed to the curved surface which contacts the arm elements 98, 100. The bores 114, 116, 118 and 120 extend only part way through the bars 110, 112. A coil spring 122, 124 is fitted between each of the bars 110, 112 of each contact arm assembly on each side of the shaft 18, with each end of the springs being seated in one of the bores 114, 116, 118, 120 so that the springs are dis posed parallel to each other and perpendicular to the bars 110, 112. The springs 122, 124 are under tension and urge the arms of the contact leaf outwardly to the limit imposed by the clamp element 102.

The contact surfaces 126 of the plate 12, which are to be in contact with the contact leaf arms 98 when the switch is closed, each have a beveled edge surface 128 at the edge where the arms 98 initially make contact with the surfaces 126.

The contact leaf assemblies are assembled by slipping a contact leaf element 92 along the shaft 18 and against a stop plate. The sleeve 90 is then slipped over the shaft 18 and against the leaf element. The pressure bars 110, 112 and springs 122, 124 are then inserted between the upper and lower arms 100, 98. The arms are then compressed and the clamp element is disposed adjacent to the ends of the arms with the flanges of the clamp element retaining the ends of the arms from expanding outwardly. The contact leaf element of the next adjacent contact leaf assembly is then slipped over the shaft 18 and abutted against the clamp element 102 of the previous assembly, and the next leaf assembly is completed as described above.

After the final contact leaf assembly is assembled, a stop plate is fitted over the shaft 18 and disposed against the clamp element of that assembly, and then is secured to the shaft 18 to prevent movement of the assemblies with respect to the shaft.

The switch is shown in the off position. That is, the shaft 18 has been moved to carry the leaf contact surfaces away from the contact surfaces 126 and put them over the depressions 24 in the contact plate 12.

Advancement of the piston 76 away from the cylinder 78 results in the shaft 18 moving the contact leaf assemblies 20 into contact with both the contact plate 14, with which they are always in contact, and against the surfaces 126 of the contact plate 12, thus completing the electrical circuit across the two contact plate through the contact leaf assemblies. The beveled surface 128 assists the contact leaf arms to compress slightly as the switch is closed, thus helping assure good mechanical and electrical contact across the switch.

The above described switch has high current carrying capabilities, may be oil filled and cooled, requires little bus-connecting hardware, since it is compact and may be mounted close to the electrolytic cell or other device to which it is coupled, is simple to assemble, and easy to operate either as a single unit or with several units ganged together.

The long, clean contact area of switches in accordance with this invention presents less resistance, thereby reducing power costs.

Four switches made in accordance with this invention which have each had seven contact leaf assemblies handle 28,000 amperes at an open circuit voltage of 4.5 volts with a drop across the switch in closed circuit of 12 to 30 millivoits. This is equivalent to 1,000 amperes per contact or 2,000 amperes per square inch of cross sectional contact.

What is claimed is:

1. Electrical switching apparatus comprising (A) a first contact plate, said first contact plate having a flat surface and being rectangularly shaped;

(B) a second contact plate, said plate being rectangularly shaped and having alternate co-planar contact surfaces and depressed areas disposed along the length of said second plate and disposed transversely to the longitudinal axis of said second plate;

(C) a frame element having side and end walls, an open interior, said frame element having a flat top surface and a flat bottom surface, said top and bottom surfaces being parallel to each other, said frame being disposed between and secured in liquid tight relationship to said first and second contact plates with 'said fiat surface of said first plate and said contact surfaces of said second plate facing each other, said first plate being electrically insulated from said frame element;

(D) an array of movable contact leaf assemblies, said array being disposed between said first and second contact plates within said frame element between said first and second contact plates, each of said assemblies surrounding a centrally disposed shaft which extends longitudinally through said frame element in slidable relationship therewith, the number of assemblies being not more than the number of contact surfacede'pressed area pairs in said second contact plate; said contact leaf assemblies each comprising an elongated contact leaf element having a generally C- shaped transverse cross sectional configuration in which the base part of the contact leaf has a bore extending therethrough which is adapted to fit over said shaft and in which the arms of said contact leaf element each has an arcuate part which presents a convex surface towards the contact plate adjacent to it, each of said contact leaves being shorter and less wide than one of said depressed areas, clamp means for limiting the maximum spacing between said arms, said clamp means being carried on said shaft, means carried on said shaft for limiting the minimum distance from said clamp means to the base part of each contact leaf, a pair of pressure bars, each of said pressure bars having a curved surface adapted to mate with and extend across the arcuate part of the arm of a contact leaf element on the side thereof which is remote from the adjacent contact plate, and compression spring means interposed between said pressure bars on each side of said shaft, each of said assemblies being held in fixed positional relationship along said shaft, said contact leaf element contacting both of said contact plates when said shaft is moved to one predetermined lengthwise position but contacting only one contact plate when said shaft is moved to another predetermined lengthwise position.

2. Switching apparatus in accordance with claim 1, wherein means are provided for introducing fluid into and withdrawing fluid from the interior of said frame element.

3. Switching apparatus in accordance with claim 1, wherein said contact surfaces of said second contact plate are each beveled at an edge adjacent to corresponding adjacent depressed areas.

4. Switching apparatus in accordance with claim 1, wherein said contact surfaces of said second plate, said flat surface of said first plate, and said contact leaves are metal.

5. Switching apparatus in accordance with claim 1, wherein said shaft extends through at least one end wall of said frame element in sealed relationship thereto.

6. Switching apparatus in accordance with claim 1, wherein means are provided in said pressure blocks for retaining ends of said compression spring means therein.

References Cited UNITED STATES PATENTS 3,336,556 8/1967 Henriksen ZOO-16 ROBERT K. SCHAEFER, Primary Examiner.

J. R. SCOTT, Assistant Examiner. 

